0x800F0A12 error when installing Win 7 SP 1 on dual boot machine

Here’s what I’ve got

• I have a machine with two hard disks; on one there’s a Fedora (15) install and on the other Windows 7
• I’ve got Grub set up to allow me to boot from either

And here’s the problem

• The other day I fired up my Windows 7 install for the first time in a loong time and it wanted to install Service Pack 1 (SP1)
• The install failed with nothing but an “0x800F0A12” message…not very helpful

The fix

The problem (as I found out from here) is that the service pack install requires the active boot partition to be the one with the Windows 7 install on. In my set up that partition is where the Grub loader lives so when the install checks the active partition it fails.

The article I’ve linked to outlines a solution involving the use of the Disk Management tool and DISKPART utility but there’s a simpler way to do this (at least in my situation).

• Open the Disk Management tool (Computer->Manage->Disk Management)
• Select the Disk/Partition on which your Windows install resides
• In my case this was on Disk 1, Disk 0 was where the Grub loader and Fedora installs lived.
• NOTE: The Disk Management tool will show which partition is “Active” and, since you’ve got the error, that will not be the one where Windows 7 lives. Check this: if your Windows 7 partition is Active and you still get the error then there’s something else going on…
• Mark it as “active” by right clicking on it and selecting “Mark Partition as Active“
• You’re done

You will now have TWO (2) partitions active; one which is the one you had from before and one which is where Windows 7 lives. It doesn’t matter if you’ve got two, all the “marking as active” operation does is to inform the firmware that the partition can be booted from, not that it will…

You can now proceed to install the Service Pack 1.

In my case it all worked.